The present invention relates to parachutes, and more particularly, to a gliding parachute of the flexible airfoil type having an improved suspension line attachment structure which provides better stress distribution while reducing weight and bulk.
For many years parachutes have been constructed by sewing a plurality of panels together to define a hemispherical structure when inflated. Some of these dome-like parachutes have incorporated slits, vents or baffles for controlling the flow of air therethrough, both to facilitate deployment and to provide maneuverability. However, these parachutes are adapted primarily for nearly vertical descent, and generally do not permit a load to be guided over substantial horizontal distances to a target landing area.
Recently, gliding parachutes have been developed for sport jumping, fire fighting, and military applications which can be readily manipulated to carry a load over a substantial distance. A typical gliding parachute is preformed and constrained in such a manner that when inflated it will define an airfoil in longitudinal section. When a load is suspended from this type of inflated parachute, the parachute will glide forwardly and its airfoil shape will provide the necessary lift. By controlling the peripheral edges of the gliding parachute, the parachute and the load can be guided in their path of descent to a target many miles away from the drop point.
Much emphasis has been placed on the fabric and rigging configurations of previous gliding parachutes in an effort to approximate, as close as possible, a conventional airfoil shape. This results in maximum lift for a given chute area which in turn provides the maximum glide ratio.
In a multi-cell gliding parachute upper and lower fabric canopies are connected by laterally spaced fabric ribs. Suspension lines are connected at their upper ends to the parachute and converge downwardly to a harness or other load supporting structure. The fabric sections of the parachute are normally made of a high strength, lightweight fabric of suitable porosity, such as that sold under the trademark F-111 RIPSTOP NYLON. These sections are typically connected by stitching their adjoining edges together with strong thread.
The manner in which the suspension lines are attached to a multi-cell gliding parachute is very important because it is the means by which the load is supported. The attachment structure must be strong enough to withstand the forces encountered during deployment without ripping the fabric or disconnecting a suspension line. Also, the attachment structure must be designed to constrain the canopies in such a manner as to produce the desired airfoil shape. However the suspension line attachment structure must not add an undue amount of weight or bulk to the parachute since it must be tightly packed in a small enclosure and carried by the jumper prior to deployment.
Heretofore different approaches have been used in attaching the suspension lines to the parachute. U.S. Pat. No. Re. 26,427 of Jalbert discloses a gliding parachute including an upper canopy and a bottom planar skin connected together by a plurality of vertically extending, spaced apart ribs to define longitudinal channels through which air flows to sustain a conventional airfoil shape. Connected to the bottom skin of the parachute are a plurality of fabric wedges which provide for even distribution of the forces of the suspension lines to the bottom skin to permit it to retain a flat configuration during flight.
U.S. Pat. No. 3,724,789 of Snyder discloses a gliding parachute of the multi-channel type in which the suspension lines are secured to the airfoil-shaped ribs between the upper and lower panels of the wing with a plurality of reinforcing tapes to distribute the load. In the Snyder parachute the reinforcing tapes are stitched to the fabric ribs. These tapes extend across the full height of the ribs and are connected directly to spaced locations on the upper canopy. A plurality of such tapes is used to connect each suspension line to a corresponding rib. The tapes associated with each suspension line extend across the corresponding rib in diverging fashion from their point of connection with the tape.
U.S. Pat. No. 4,399,969 of Gargano discloses another multi-cell gliding parachute in which the suspension lines are connected to the ribs by single reinforcing tapes which are stitched to the ribs and extend the full height thereof.
U.S. Pat. No. 2,365,184 of Frieder et al. discloses a special hem construction for lessening the likelihood that stitching will rupture from loads applied through the shroud lines. Only a section of the parachute is illustrated, however, it is assumed that it is of the single canopy, hemispherical type widely used during World War II in view of the filing date of the patent. The peripheral edge of the canopy is folded around a reinforcing cord and stitched. At each side of each point where a shroud line is connected are two tapes stitched to the canopy, the tapes of each pair crossing under the hem adjacent to the opening through the hem through which the reinforcing cord is exposed. FIG. 4 of Frieder et al illustrates a single tape version of the special hem construction.
Whatever the form of the fabric portion and rigging previously employed in a gliding parachute, there has been a tendency for the shape of the inflated wing to depart from the desired conventional airfoil shape. The various fabric and rigging constructions which have heretofore been utilized in gliding parachutes in an attempt to maintain the conventional airfoil shape have added to the weight and complexity of the parachute.
For example, the fabric wedges or flares of the Jalbert parachute described above provide a good deal of load distribution that lessens the chance of rupturing stitching or disconnection of a suspension line. These flares also aid in distributing the load over the canopies in a manner that preserves their desired airfoil shape. However these flares add considerable weight and bulk to the parachute.
The suspension line attachment structure of Snyder results in bumps or puckers in the upper canopy. This lessens the efficiency of the inflated airfoil resulting in increased drag and less lift. The use of multiple reinforcing tapes for each suspension line also adds to the bulk and weight of the parachute.